In order to reduce the influence of vibration, such as image shake, on an image, a correction optical system has been shifted or tilted in prior arts. For example, a first method of shifting or tilting the correction optical system is shifting the correction optical system in a direction perpendicular to the optical axis of the objective optical system (e.g. see Patent Document 1). In this method, the image-shake preventing mechanism can be simplified, but a change in and deterioration of the image caused by the shift of the correction optical system are significant, hence the correction angle must be set to a small value in order to maintain good optical performance. If the correction angle is set to a large value, a major change in the image, due to a shift of the correction optical system, must be allowed.
A second method of shifting or tilting the correction optical system is oscillating the correction optical system in a direction perpendicular to the optical axis of the objective optical system (e.g. see Patent Document 2). In this method, change in the image caused by the oscillation of the correction optical system can be controlled, but because of this configuration of the objective optical system, the optical performance drops from the original optical performance due to the oscillation of the correction optical system, which makes it difficult to increase aperture.
A third method of shifting or tilting the correction optical system is rotating the correction optical system (e.g. see Patent Document 3). In this method, a change in the image caused by the rotation of the correction optical system can be controlled, but the correction angle decreases. To increase the correction angle, the correction optical system must be further rotated, which increases the size of such optical devices as a telescope and a binocular telescope.